A. Field of the Invention
The present invention relates to the testing of navigation and/or positioning equipment. As used herein, navigation and/or positioning equipment refers to any positioning, surveying, anchoring, timing or tracking equipment and systems. More particularly, though not exclusively, the present invention relates to a test facility made up of a precisely constructed elevated track upon which one may test the accuracy of navigation or positioning equipment through the use of a test bed vehicle.
B. Problems in the Art
It would be highly beneficial to such things as farming if a tractor could be autonomously controlled, without the need for a human operator. A navigation system would be needed that would be able to precisely control operation of the tractor through a field. It would have to avoid both missing parts of a field and overlap when working a field, as well as avoid physical structures such as fences, trees, creeks, etc.
Some prior art systems that are trying to develop autonomous navigating vehicles utilize physical structures placed throughout the field so that the vehicle can sense the vehicle""s relative location to the physical structures. Building and distributing such physical structures throughout vast areas is very costly.
Global Positioning Systems have become widely used. While some people believe that global positioning systems could be used for autonomous navigation systems, a significant problem exists. There is a latency problem with GPS. In other words, if the GPS receiver is stationary, the GPS signal coming from the satellites can be used to very accurately locate that person on the surface of the earth. However, if the GPS receiver is moving, and especially if moving at more than very slow speeds (greater than 10 miles per hour) by the time the position is determined, the vehicle has moved a substantial distance. Therefore, with GPS one would know where one was on the face of the earth a few seconds ago, but not where one is right now. If a tractor is traveling at 10-15 mph, this is a very meaningful distance and therefore a very substantial inaccuracy can exist between actual position and GPS calculated position. Therefore, some parties are attempting to use correction schemes to correct for that latency error.
Other navigation systems, such as inertial-based systems, are in use. Inertial systems have a problem of drift. Over time, they lose accuracy unless reinitialized. Therefore, while very accurate over a short period of time since the last known position, accuracy degrades as time passes.
Because of the large amount of activity in trying to create a very accurate navigation system for moving vehicles, a real need in the art exists for a way to verify whether the developed navigational systems are indeed accurate. Many claims are made to accuracy, but it is difficult to verify whether a navigational system, submitted to various speeds, will retain its accuracy over time.
C. Features of the Invention
A general feature of the present invention is the provision of a system, apparatus and method that solves the problems in the art.
Another feature of the present invention is a system that uses a test facility including a test track upon which a test vehicle may travel, which allows for testing of navigational equipment.
A further feature of the present invention is the provision of a test track where the length of the track and elevation of the track are precisely known.
A still further feature of the present invention the provision of a test track in which the orientation of the sections of the track may be known with respect to the cardinal directions (north, south, east or west). More precisely, the track may have a known azimuth.
Another feature of the present invention is the provision of a test track in which sections of the track may be precisely aligned north to south.
A further feature of the present invention is the provision of a test track in which sections of the track may be precisely aligned east to west.
A still further feature of the present invention is the provision of a test track in which sections of the track could be precisely aligned south-east to north-west.
A further feature of the present invention is the provision of a test track in which sections of the track could be precisely aligned south-west to north-east.
Another feature of the present invention is a test facility which may include stations, which can provide calibration points for elevation and location.
A still further feature of the present invention could include curved portions of the track, which could spiral under and over one another to test whether the navigational system can double back upon itself and remain accurate.
A further feature of the present invention is the provision of a test vehicle in which one or more pieces of navigational equipment may be placed and subjected to test under the same conditions.
A still further feature of the present invention is the provision of a test vehicle that may be capable of traveling along the test track in a repeatable manner along a precisely known path.
Another feature of the present invention is the provision of a test vehicle that could acquire data necessary to determine its actual position at any point on the test track.
A still further feature of the present invention is the provision of a test vehicle that may be capable of varying speeds.
An optional feature of the present invention is the provision of a multiple degree of freedom of movement frame, which may be connected to the test vehicle and to which one or more devices under test may be connected.
A further optional feature of the present invention is the provision of a multiple degree of freedom of movement frame that could be capable of controlling the attitude of the devices under test.
A further feature of the present invention is the provision of a multiple degree of freedom of movement frame that is able to change the altitude of the devices under test.
A still further feature of the present invention is the provision of a multiple degree of freedom of movement frame that could be able to change the cross-track position of the devices under test. Specifically, it could be able to offset the device under test perpendicularly to the direction of travel.
Another feature of the present invention is the provision of a monitoring system, which may allow the user of the test facility to see data in real time.
A further feature of the present invention is the provision of a monitoring system that may be capable of recording both the actual position, speed and heading of the device under test and the data reported by the device under test.
A still further feature of the present invention is the provision of computer programs, which can be capable of executing a test and displaying results in real time as well as post processing.
These as well as other features of the present invention will become apparent from the following specification and claims.
The present invention relates to a method and apparatus for testing the accuracy of navigation or positioning equipment. A test track is provided with geographic location, orientation, track elevation, distance, attitude, and altitude known for any point on the track to within a fraction of an inch. The test vehicle, including the navigation or positioning equipment to be tested, i.e. the device under test, is adapted to be placed upon the track. The test vehicle is adapted to move along the track and the navigation or positioning equipment can be operated to indicate the test vehicle""s position, attitude, elevation, or other desired parameter which is then compared with the actual known parameters of the vehicle on the test track. The test vehicle may be operated automatically or manually. In the automatic mode of operation, a user can use a pre-programmed or stored program to repeat a test for many devices under the same conditions. A manual mode of operation allows the user to perform random testing.
Optionally, the user of the apparatus can selectively test the sensitivity of the navigation or positioning equipment to attitude adjustment, overlapping tracks, and other environmental concerns. The test track may also be used to continually operate a test vehicle so as to test maintainable accuracy and endurance of the navigation or positioning equipment.
All of the data reported by the test bed vehicle and the navigation or positioning equipment under test is reported to a central computer. The computer allows the user to view data in real time as well as record data for further analysis and study.